Tony's Dungeon

RESEARCH:

DEERSLAYER LINKS including vendor sites for parts and tools as well as sites for old truck and hot rod organizations

HISTORY:

TINKERING WITH DEERSLAYER chronicles the day-by-day maintenance and improvements episodes for Deerslayer, a '37 Chevy farm truck hot rod.

CRUISIN' WITH DEERSLAYER Roadtrips, cruise-in's and truck show stories and tall tales.

TONY'S DUNGEON Tony Pascarella's forum entries at OldGMCtrucks.com and H.A.M.B. regarding Deerslayer, particularly the 302 GMC engine build in his farmhouse basement.

MAINTENANCE:

DEERSLAYER MAINTENANCE Ever changing detailing, oil change, lube, etc. maintenance routines specifically developed for Deerslayer, including required tools, materials and procedures.

PROJECT NAILHEAD Chronicles the rebuild of a 1954 Buick Roadmaster 322 nailhead engine as a future replacement for Deerslayer's Jimmy 302.

When Tony put up the truck for sale, he offered this seller's description: "This is a 37 Chevy PU highly modified but retains a somewhat stock appearance.All steel,except for fiberglass fenders,the bed is very nice,the cab is solid,no rot,but a few old small dents are still seen here and there,the running boards are solid but show some slight damage typical to trucks,epoxy primer paint job is 10 years old,looks respectable.The interior is stock except for a decent fitting mini van bench seat,stock gages all work plus a tach.No radio or heater.The stock front axle has Camaro disc brakes,mono leaf springs,sway bar,gas shocks . Frame is not cut.The rear axle is a 57 Chevy car,3.36 gears,leaf springs ,lowering blocks,Panhard rod,gas shocks. This truck sits about 2-3 inches lower than stock.46 Chevy steering box. All glass and rubber parts replaced 10 years ago,has a working electric wiper and turn signals,halogen headlights,12 volt GM alternator The engine is a 56 302 GMC inline 6,Venolia 9.25 forged pistons,3/4 hot cam,small block V-8 valves and springs,home made tube headers,400 cfm Carter AFB,balanced,HEI ignition,much more,runs very smooth and powerful but does require premium fuel.Camaro 5 speed transmission,Hayes clutch etc. This truck runs straight down the road,handles better than most ,the ride is firm and controlled,not bouncy or harsh,can cruise all day at 70 mph,2100 rpm.Doesn't rattle or shake. It's built to my taste,very basic,nothing fancy,very little store bought parts.I built the truck 10 years ago ,it was powered by a Chevy 6 until I built the GMC engine 3 years ago.Truck is always been stored indoors.It can still function as a truck,has a receiver trailer hitch and can carry a load if necessary."

What follows is some of the skinny on how the truck got to where it was, in the builder's own words, when it came to me.

BED

Posted Thu May 22 2008 03:10 PM I bought bedsides,a front panel and tailgate for my 37 Chevy about 10 years ago from Mack Products.All decent quality and it was galvanized.You have to prep the galvanized metal as mentioned above. I susggest mocking up the bed befor you apply primer ,might have to make a slight adjustment here and there,ya know a little trimming or grinder work.

CAMSHAFT

Posted Thu January 26 2006 05:49 AM Awhile back,the US auto makers petitioned the oil manufacturers to remove or severely limit the amount of sulfur in motor oils.The sulfur,found in the minute amounts of oil getting past the rings and valve seals,was ruining catalytic convertors,which is a warranty issue for the vehicle manufacturer.The sulfur was or is the most effective additive able to handle high load pressure,like found where a flat tappet lifter contacts the cam lobe.Since most newer engines have roller lifters ,this isn't a big deal. Now,according to the local machine shop I use,this can be an issue in older engines,especially when hotter cams and higher spring pressures are used on flat tappet cams.He claims the lack of sulfur in oil may lead to cam lobe failure during the critical break in period despite the use of sticky moly cam lubes. You can smell the suflur when you open a bottle of gear oil,same for Diesel oils and racing oils. The shop uses 15-40 Diesel oil for breakin purposes on the engines he sells completely assembled,ie, small block Chevy V-8's with a moderate performance build up.And he recomends it for any rebuild.The Diesel oil has a much higher sulfer content,as does most 20-50 racing oils.He went on to say,you shouldn't use the 5-30 and 10-30 oils with the starburst symbol in older engines at any time.But the old 6's have low pressure valve springs and large diameter lifters,so a stock rebuilt old GM 6 shouldn't care much about oil and sulfur ,maybe . I'm sure there's many opinions on this,but this shop builds hundreds of engines a year,has to guarantee them,so...........

Posted Thu April 06 2006 08:19 AM After my recent fiasco with wiped out cam lobe I did some research on the matter. Zinc levels in motor oil were lowered to about nothing a few years back.The US auto makers petitioned the oil companies to eliminate the zinc to prevent warranty claims on cat convertors.A small amount of oil getting past the rings or valve guides can foul the convertor.As usual,instead of designing better ways to prevent oil burining,the auto makers took the easy way out. So....when this happened,performance cam grinders got a rash of warranty claims from new cam failures.They found it was the lack of zinc,the zinc is a high load additive,it protects the cam and lifters from galling,especially on new cam breakin. Modern engines have roller lifters and don't need the extra zinc protection. I had conversations with quite a few cam grinders,some said use 15-40 Diesel oil,but I can't find any info stating the diesel oils actually contain higher zinc levels. However,Valvoline's own website claims it conventional racing oils,all grades,have added zinc for cam protection.The racing oil is not recomended for street use cause of lower detergent levels. The recomendation,at the least,is to fill the crankcase with Valvoline racing oil,the lightest grade is 20/50 I believe,for the cam breakin procedure.Then after you change the oil you can mix in the racing oil with a regular oil if needed.Or continue to use the Valvoline racing oil since the lower detergent levels shouldn't be an issue with the way most older vehicles are driven. In additon,GM makes a oil supplement,part number 1052367,it's got high zinc levels and recomended by GM when installin a Goodwrench hi performance camshaft.This product is designed to be added to your normal 10/40 type oils. The GM supplement can be had at any GM dealer or I bought a few quarts,5 bucks each, from GM parts direct online. This zinc bullshit is usually an issue only on performance cams,stiffer springs and flat tappets.Stock type cam amd old lady valve springs shouldn't cause a problem,but you may want to play it safe.

Posted Thu April 06 2006 05:44 PM Andy,I've heard some toot their horns about the JD oil.Does it mention any additives on the can or on a website? 168 lbs at your engines maximum lift?Ya got the balls to pop the side cover,pull a few lifters and check em for wear? After all this shit,I'm so parinoid about cam wear,I'll probably zinc the engine to death.Maybe throwing an old Rochester carb in the oil pan will release enough zinc. Yeah,the GM supplement,I was shooting the breeze with Pat Dykes after buying lifters,he also took a hit one some cams a few years back. EnsoniqMan,thanks for the link,I'll check it out.Hopefully those guys have actual real world experience with lubes,text book oil analyzing don't help the cam out any. Just for fun,Crane Cams can do a one off billet roller cam,about 600 bucks.Then you buy custom roller lifters,another pile of dead Presidents.Then you need to machine the block for lifters,machine the crank to clear the big lobes,then you discover the lobes are too big to get past the cam bearings.

Posted Fri April 07 2006 05:23 AM One thing for sure,none of the cam grinders I talked to blamed too stiff a spring as the sole thing responsible for wiping the cam.They said the springs I used were heavier than necessary,but within the design limits of a reground cast cam with large .975 diameter lifters. This wasn't the first cam I installed,only the first to fail.

Posted Mon April 24 2006 04:18 PM A call today from Lazer Cams,the shop doing my new regrind,the NOS military 302 cam I sent him has no taper on the lobe high point.It's straight across,I don't know if all GMC cams are that way.Lazer told me all performance cams need tha taper along with the cam lobe offset slightly in relation to the lifter center line.On GMC's,the cam is offset towards the front. The taper and zinc is the key to a happy cam I guess.

Posted Fri May 12 2006 06:04 PM I notice Castol's reply mentions "vintage engines built to historic specifications" Nice,but the cam wear problem is primarily,in my observation, from older flat tappet engines with performance cams and springs.Vintage engines,the stock ones dicussed here,have low pressure valve springs and very mild camshafts,you could probabaly wipe my half Italian head on the cam and get enough lube protection. Like mentioned above,play it safe,use the proper oil reguardless of engine tune.

Posted Mon May 19 2008 05:43 PM Ken,the first set of springs I used when my engine's cam wiped out was the so called Z-28 springs you sent to me,same pressures as you're using. I asked the guy that did the machine work if the pressures were to high.He said no they aren't even considering a reground cam and the relatively low rpms of the GMC 6's.Although he disagreed with me,I went with less spring on the second cam,same closed rate,and 220 lbs open. I hear it used to be common place to break in radial flat tappet cams with wimpy springs.I'm talking about cams with over .600 lift and mega duration. From what I read,the nearly one inch diameter GMC-Chevy lifter allows faster lift rates and is generally easier on the cam than the smaller diameter lifter found in V-8's and the later L series 230-292 6's. Can we say roller tappets? Ken you got the specs on your cam,duration at .050 lift,cam lobe lift,lobe centers?

Posted Tue May 20 2008 07:09 AM Cam comparisons are interesting.The Lazer grind in my 302 has 215 degree degrees at .050 lift on both intake and exhaust,112 lobe centers,.425 actual lift at the valve figuring the rocker ratio is 1.41 as I measured it.Sounds similar but I don't have advertised lift for my cam..Advertised duration is generally taken at .004-.006 lift.My cam is a "tight lash" design,only .004 hot valve lash intake and exhaust compared to the usual of around .015 ish.The tight lash supposedly gets the valve off the seat very quickly. Anyways,this winter I pulled the lifters for an inspection after about 3000 miles on the cam.The lifter faces had a very slight polished circular wear pattern,no scratches or pits.I'm using the springs like Ken's,it's a cast cam with Chevy 235 style lifters.I painted a stripe on the pushrod,so with the valve cover off,engine running,I can see the pushrods spin before I do the valve lash check.All pushrods spinning the same,all is well,no spinning,go in the house and cry I'm a little parinoid after my cam failure.It failed big time with debris in all the bearings despite the full flow filter.I had to break down the entire engine,clean it all out,all new bearings,lightly hone the cylinders and new rings. If you look at cam specs and recomendations for V-8 engines with 400 cubes,similar per cylinder displacemnet as these GMC's more or less,you'll see our cams are actually not much different than the typical 350 HP V-8 muscle car OEM cam grinds of the 60's,except they were hydraulic flat tappet.

Posted Thu September 18 2008 04:26 PM When the cam failed after about 500 miles on my 302 there was metal shit embedded in all the bearings despite a full flow filter.I tore down the engine to a bare block,cleaned it,a light hone on the cylinders with new rings and bearings. After a new another reground performance cam,zinc in the oil,a lifter check showed everything looking like new after a few thousand miles. With flat tappets paint a line on each pushrod to check for spin with the engine at idle when adjusting the valves.

CARBURETOR

04-05-2008, 04:42 PM I got this modified GMC 302 inline engine,I had a Holley 390 cfm 4 bbl on it.ran quite nicely,no bogs or flat spots.Well,I loaned the Holley to a friend to try on his engine,he liked it and bought if.I wanted to try a different carb anyways,got my hands on a 400 cfm AFB 9400 series 4bbl .I figured it would need some jetting changes,disconected the secondary linkage for testing.Got the primary jetted up real nice,good idle,great throttle response,engine pulls cleanly from idle to redline,impressive for 200 or so CFM.This engine has a water heated intake. So I reconnect the linkage for the secondaries to sort out the jetting.Hmm,no so fuckin good,the typical big bog as ya floor the pedal at about 2500 rpms.Then the engine catches and takes of real strong.I jetted up the secondary about .007,a little better.Then I pulled the counter weighted secondary air flap,welded up metal to make it heavier ans sloer to open so to speak.Again a small improvement,but still the stumble when the throttle is opened suddenly.If you sneak up on full throttle it's almost tolerable.I checked the carb parts numbers of the venturi clusters,air bleeds and so on,all are correct,appear to be unaltered.In fact this carb is almost new actually. I even tried primary metering rods with way richer power step,no improvemt at full throttle and for sure made the primary too rich when pulling hard at part throttle. I'm no carburation expert but I've never had problems with getting jetting close enough.It's hard to believe this smallest of AFB's acts like it too large,but the 390 Holley was fine.Maybe it's just the Holley vacuum secondaries just work better? I suppose I can jet the AFB secondaries even richer but experience say if you need to rejet more than 6 or 7 sizes the carb is wrong for the application.Again,400 cfm should be spot on for a 302 GMC with cam ,header,and all that stuff.

04-05-2008, 05:14 PM I checked for leaks and since the engine idles ok and responds to turning the idle mixture screws,must be ok. The timing curve is fairly aggressive,12 degrees initial,34 total at about 2800 rpm,HEI distributor with a vacuum advance.

04-06-2008, 07:09 AM Thanks for the suggestions. I did mess with the metering rod springs,I'm using the springs rated for 6 inches of vacuum.I think a larger accelerator pump nozzle will exhaust the pump supply quicker? The engine for sure seems like it goes lean for a moment when the secondary is opened.But it "sounds" different than other 4 bbl lean outs I 've experienced.it's a studder sound,then the engine grabs hold,almost like a brief sparkplug misfire than the typical "flat" sound of a leanout.My plugs are gapped for .045 with the HEI.This gap worked ok with the Holley.For kicks,I'll gap the plugs back to .035.The ignition seems fine,spiral wound low resistence wires,quality coil,non resistor plugs.The cam I'm using builds a lot of cylinder pressure at mid speeds,low manifold airflow and poor vaporization when the secondaries open,and 9.5 actual compression might be a big load for the ignition to fire? It runs so strong on the primaries I might be tempted to leave the secondaries disconnected and forget all this tuning headache Some guys don't like Holleys,I'm thinking the Holley is more forgiving of engine tuning than an AFB type carb.

04-06-2008, 09:24 AM So,I just regapped the plugs closer,took a ride,another small improvement.Then I stuck a thin wire in the secondary venuri cluster air bleed hoping it will create a stronger vaccum signal to the booster and pull fuel earlier.Another small improvement.But the bog is still there to some degree,not too bad in lower gears,but worse in high gear on the hiway. I have a brand new Holley 500 cfm 2 barrel in the box,maybe I'll swap on the big two barrel and be done with it.It's looking more like this Carter 400 cfm 4 bbl just don't like my engine.............

CLUTCH

Posted Wed July 23 2008 04:20 PM Clutch grip depends more on clutch cover pressure and disc material than the clutch diameter.And many newer or retro fitted performance vehicles use a small diameter multi disc set up,kinda like motorcycles do.As mentioned aboved,the smaller diameter is better with fast shifts at high rpm's. Some of you may remember winding the shit out of a 283 or 327 and having the stock diaphram clutch refuse to release after a fast shift until the rpm dropped down. The 3 finger B&B type usually have a faster release ,but to get good grip the pedal pressure can be excessive for daily driving.I don't think they will clear the stock old 6 cylinder clutch housing,same for the Long type design. My 37's stock clutch pedal linkage bent all to hell when I first put in a real clutch.I beefed it up and used Heim type joints instead of just the stock fricton prone metal on metal bent rod in hole.I think this might be a good idea on an AD truck for the one side of the clutch rod,if there's room to do it.The pedal feel and action was quite improved. Ken ,doing the "Ton" in an AD is moving right along.

Posted Wed July 23 2008 05:51 AM Ken,unless you're flywheel is drilled for an 11 inch pressure plate....it ain't gonna fit,the bolt pattern is a larger diameter. You have a 10 inch or is it actually a 10.4? A proper 10.4 inch will handle 350+ lbs of torque no problem,quite common on built smallblock V-8's.My 37's got a 11 inch Ram brand clutch.It's an OEM replacement,but has about 20 percent more grip,A little more pedal pressure and slight more aggressive disc lining,slight chatter when cold.It never slips under any conditions,nice pedal feel and engagement.Ram is made in USA,the other populat hi po unit,Zoom is made overseas.Then there's Hays for about twice the money.But I know that the 11 inch Ram diaphram will clear a 216 Chevy bellhousing or the GMC which is indentical..Order one from Summit Racing online ,and it costs slightly less than the rebuilt junk sold at parts stores.Been my experience that more aggressive clutch linings will cause chatter on 6's especially when used on open driveline conversions in old trucks with their less than ideal motor mounts. I use the universal Chevy clutch with the 26 spline,yours is 1-1/8 inch 10 spline with the A883,the release bearing is the common one in the kit.Do mock up the clutch disc against the flywheel as sometimes the disc hub just touches the crank,A hand grinder on the hub quickly takes care of the clearance issue if needed. It's also been my experience that what ever non asbestos disc lining is used on generic clutches can't handle much slipping before it's slips when ya don't want it to.

DESKTOP DYNO SPECS

Posted Sat September 27 2008 06:19 PM Larry,being I was the guy who built the engine,the estimate of about 230 HP and 300 ft lbs of torque is reasonable. The head isn't really ported.When the Chevy V-8 valves were fitted the machinist opened up the area below the valves slightly but didn't go hog wild as that upsets the venturi effect just before the valve.The ports themselves are as stock 1-3/4 inch. And the camshaft being a "tight lash " type with only .005 hot valve clearance makes the cam duration seem bigger than the listed 215 degrees at .050 lift.Otherwords the valve is opened quickly,more lift under the curve as they say.The lobe separation is 110 degrees I believe.Was the timing card from Lazer Cams in that pile of paper work shit I gave you? And there was a yellow piece of paper with my scribbling on it when I degreed the cam in.My head says the intake valve at.050 lift opened at one degree after TDC and closed at 37 degrees. GMC rods are 7 inch from center to center,more or less. Anyways, if you run it on a chassis dyno do use caution.The full throttle carb mixture is a bit on the lean side for snappy throttle response and might lead to detonation if run wide open at maxium power for an extended time. Did you install the HEI? It does make a power difference over the points dizzy.

ENGINE MOUNTS

Posted Mon May 10 2004 03:05 PM I just installed a newly introduced polyurethane fron mount for GM trucks from advanced Design Engineering. This mount was installed in my 37 Chevy pu with a modified 261.The mount looked just peachy,appeared to be good quality and good molding job.Installation is straightfoward just like the stock one, easy or difficult depending on the installer's skills and truck condition.Pay attention to the specs given in the repair manual, you may have to grind or file the metal mount enclosure for the proper clearance, which you would or should do with the stock mount anyways.The old rubber mount was as limp as a dead mans dick on a cold day, oil soaked as usual.A road test revealed less vibration, my truck's clutch didn't chatter before hand so I can't comment on that.The real test is a few years down the road to see if the new mount lives up to claims of not being affected by oil.At any rate,40 bucks for the mount is chump change, especially for outlasting the usual poor quality rubber ones for 10-15 bucks. Tony in NY

Posted Sun May 23 2004 09:05 AM I've run the mount for a few hundred miles now,the engines seems to run a tad smoother,and while the clutch didn't chatter too much on takeoff before, I have to say the clutch action is smoother. Since I changed nothing but the mount, it must be the poly mount is an improvement.Ha, even the front seal leaks less, lol.

FUEL PUMP

Posted Thu September 04 2008 07:57 PM Pumps with glass bowls are seen on both GMC and Chevy.And the pump is interchangable betweeen the two engines although the fuel ports might be "clocked" different. Some guys here run a fliter on the pump suction side with no problems,Dodge vans were like that too.But like G.M.C. says above,I think they belong on the pressure side.

IGNITION

Posted Wed July 09 2008 09:25 PM Geez Bill, I have a dual point plate for GMC-Chevy distributors sitting here on my shelf,I would have given it to ya if I knew you wanted to convert the distributor!!!! The one I have is modified to use inexpensive Ford 1960's V-8 point sets. Andy and I had a discussion yesterday on ignitions.I told him about a tech article about aircraft magnetos.A mag and also a Kettering ignition to a lesser degree ( coil and points or electronic "points") give off two types of spark.The first is a high voltage short duration Capacative spark,followed by a less intense longer duration inductive spark.If the first spark doesn't light the fire,the second longer duration spark will.Kinda like the modern capactive discharge multi spark ignitions so to speak. Well,the use of typical high resistence spark plug wires and spark plugs to kill electronic interference cuts off the second inductive spark leaving just the short initial capactive spark. Ok,so what...I tried both single and dual point distributors in the 37 Chevy's modified 302.The plugs were non resistor racing plugs,the wires were high quality spiral wound resistence conductors,500 ohm a foot compared to several 1000 ohms a foot carbon core wires..The engine always had a misfire off idle and a slight hesitation when easing down the gas pedal at moderate speeds.A milti spark box,and later an HEI cired this problem. So now Larry buys the truck.I figured he would feel more comfortable with a points set up.The HEI goes with the truck too..I had a set of solid copper core hi performance wires.I intalled the single points distributor, solid core wires,same non resistor wires and....no miss fire,it's runs exactly the same as the HEI or modern black box ignition.Obiviously all the distributors have similar recurved mechanical advance set ups .

Posted Sun September 28 2008 10:50 AM Just jump a wire across the ballast terminals.Rotate the engine to tdc,the rotor pointing at number one plug terminal so you know the crank is in the correct position.Normal engine running rotation is clockwise viewed from the front.Removing the plugs makes the engine easiy to rotate with the fan.There's two marks on the damper I scribed,as you rotate the engine clockwise the first mark is 34 degrees,the second mark is TDC.position the damper about a 1/3 past TDC towards the total advance mark.Now carefully remove the points distributor.The hei cap with wires should have a mark on the number one wire,but actually it makes no difference so long as the rotor is lined up with a terminal you'll call number one.The HEI is set up to drop in,don't disturb the clamp,it should drop right in with the clamp bottoming out on the block,lining up with the retaining bolt hole..You'll see how the rotor turns as you install the distributor,it might take a few tries,you may have to take a long screwdriver to rotate the oil pump drive a little bit this way or that so the distributor bottoms out on the clamp.Do not attemp to tighten the distributor unless it bottoms on the clamp easily,be maybe a 1/16 inch clearance between the clamp and block.Install the clamp bolt and snug it down in the middle of the adjustment slot.Now see where the rotor points and check the cap,call that number one and do the wires so they reach properly in the firing order ,clockwise,153624.Now remove the coil,install the funky looking HEI coil.The big black wire that was on the cannister coil positive goes to the HEI coil terminal marked positive.The red wire on the cannister coil negative terminal is for the tach,put that on the HEI coil negative.There's a small wiring harness that plugs into the two short HEI distributor leads,the lead with black tape goes to coil positive,the other to negative. Ok,should start right up,leave off the vacuum hose.At idle the timing will be about 1/3 the way up from on the damper TDC mark.More important on this engine is to check full advance.Rev the engine quickly to 3000 rpm or so and you'll see the timing mark advance then stop at full advance.You're using a timing light of course,lol.That gets set on the second mark,34 degrees.There's also a 34 full advance mark on the flywheel visable in the normal timing position in the clutch housing hole above the starter. Let me know if you have any issues, Tony

MACHINE WORK

Posted Wed November 30 2005 09:34 AM Looks like the crack is beyond range of the seat replacement machine work.And the crack may reappear even if machined away.A bummer Kook. I was lucky on my 302,no cracks.I had the machine shop Magnaflux and pressure check the head before doing the machining for replacement seats and modifing the valve ports for small block Chevy valves.The block was also double checked.The machinist spend some time closely checking out the crank and rods for signs of fatigue. Rob,make sure you have the rods resized if it hasn't been brought to your attention already ,it's relatively inexpensive,sort of, and worth every penny to have the correct bearing crush and the rods running true.

MAIN BEARINGS

Posted Wed February 09 2005 11:00 AM You may know I've been looking for Clevite 77 .010 main bearings for my 302 engine.Seems the supply has dried up,as well as King and Vandervall.The option was to go for Federal Moguls,made in Mexico,I don't care for the look or fit for a performance engine. . After some detective work,I found a good supply of Michigan brand bearings,they are the tri metal design same quality as Clevite.In fact Clevite bought out Michigan bearing back when The shop with the supply of bearings is Mills Motor parts in Louisana, 800-624-7999,ask for Mike.They are 150 bucks a set,the going rate for Clevites.

OIL PUMP

Posted Fri August 15 2008 03:42 PM Ken,my signature is the pick tube for the oil pump,Tony made anti- votex "box" on the tube rather the the flat pan. Yeah,the engine sound attracts attention when gear heads hear it.Sharper guys reconize the inline song,others think it's some sort of off beat V-8.Joy says it sounds like a UPS truck on crack.

PERFORMANCE

Posted Thu July 31 2008 08:53 AM I'm no expert on engine tuning but I have a lots of books written by pro engine builders.....and some backyard experience on a few inlines and cycles I did spend a lot of time on my modified GMC 302 doing jetting on the various four barrel set ups I used.I found that GMC's need a fairly rich mixture at full load,especially at around 2500-3000 rpm where the torque curve peaks on a typical modified engine.otherwords the GMC requires more fuel per HP than the typical V-8 that the 4 barrel carbs are normally used on.This mixture needs to be a little leaner once the engine winds up near HP peak.Hard to do with carbs Plug readings are always difficult,modern fuel and high energy ignitions tend to burn away the plug color from what I've read and seen myself.Plug readings are a guestimate and the final judgement should based on acceleration times and how it feels and sounds. Champion spark plug tech reps used to or still do spend time at race tracks,they carefully inspect the working end of a spark plug with a magnifying glass and bright light.The're not looking at plug color so much as the signs of detonation,the tiny balls or specks of piston aluminum,sometimes a purple color.Lean mixture makes better cleaner power until detonation becomes a factor and you speak of your pistons or crank as "used to be". Those RX-5's may not be correct for your high compression engine.I used NGKR5670-7 a colder extended tip non resistor racing plug.About the same as a AC 42,but they never fouled in city driving with proper jetting and a hot igniton system on my engine.You can check NGK plug charts on line if you feel you wanna try a plug a step or two different than what ya have now . On the idle richness,I'm not familar with your carbs,but they are likely to be like others,the idle mixture screw won't correct rich or lean if the idle restriction jet or orfice is supplying the wrong emulsified mixture cause of engine modifications..For this ya have to mess with idle fuel restriction.This brings us back to the engine vacuum discussion with muliple carbs.The manifold vacuum is the same below the throttle plates,but the air flow through the carb venturi and the vacuum or pressure differential is reduced with two carbs as compared to the same unit on it's original single carb application.So the vacuum signal to pick up fuel from the low speed jets especially is upset.This can't always be corrected and a compromise may be necessary. Ya think ya might need port fuel injection to over come carb limitations?

Posted Fri August 01 2008 07:52 AM Mountain,what's changed is ignition systems,better spark,better sparkplugs.I like NGK pluks been using them for years. if nothing else,they appear to have a finer look to them than AC or Champion. Ken,you may not need the cold plugs I use,just think that a non resistor plug may work better for you.The heat range you got shouldn't be too hot,maybe try a step colder. If your truck was 12 volts I would send you this spare Mallory Capacitve Discharge multi spark box to test out.I used it with single points,but it's compatable with electronic trigged ignition too. In my opinion,and I could be wrong,Ken and Pete might be shoveling shit against the tide using the old style distributors despite what inside of them.I don't think you're getting the spark your engine needs.Some work fine,some don't I took out the HEI conversion from my 37 so when Larry runs it back to Florida he won't have to worry if something gets funny, he'll be guessing over what's going on inside the distributor.Not that I expect anything to fail,it'll be reliable as sunrise,just a survival theory.Once there,he cam reinstall the HEI.Anyways,what I'm getting at is the 37 truck runs smooth and responds well with the old style distributor,but there is a performance difference between it and the HEI or a multi spark black box. My idea is to use the an ignition that provides the best spark,as in longest spark duration, in a modified engine so that's one thing not suspect when troubleshooting tuning issues.On a stock engine with the original distibutor, dual points or Petronix is a useful upgrade for sure.Just an opinion from this shadetree mechanic/electrician.

Posted Thu August 07 2008 03:15 PM Ken, my 302 takes a drop in power above 4200 rpm.It'll wind up near 5 grand but it's more thrash than pull.My engine has a big port 302 head,the V-8 valves but is just port matched,not really ported at all.Cams are hard to compare,but the one in my engine is similar to yours.I believe we both have the same compression,about 9.5 more or less.My exhaust is short steel tube headers and 3 inch pipe and Flowmaster noise maker.I've had a few carbs and intakes,all 4 bbls.it goes as fast as it's gonna go with a 400 cfm Carter AFB.I think multiple carbs might be better however all else being equal. Ya know,the big port 270-302 heads were something back when,however, I believe they flow about the same as a 350 small block smog head,about 40 HP per cylinder. I don't know about the stroke,many high winding V-8's have 4 inch strokes.And modern 7-8 grand Jap car performance engines have 3-1/2 srokes for a 125 cubic inch 4 cylinder.Still there's alot of heavy metal whipping around in an inline 6.The crankshaft in a 1710 cubic inch 2000 hp Allison V-12 aircraft engine only weighs a few pounds more than a 302 crank! Your engine may have reached it power peak with the set up you got.To get more pull you may need better breathing or more displacement or more rpm's.Or forced induction Me nervous when you where winding the snot out of my truck's engine 350 miles from home with traffic stopped at the redlight ahead?

Posted Sat September 18 2010 07:03 AM Both Larry and I have gotten 18-20 mpg at 65 mph in the 302 powered 37.The mileage was checked on many road trips and pretty much came out the same.Both of us report at 16+ mpg driving around town.The 37 engine pulls about 10-11 inches of vacuum at 65 mph(2000 rpm) on level ground.Intake vacuum helps atomize fuel but more important if your cruise vacuum falls low enough,the power valve may open.The 37 is maybe 300 pounds lighter than an AD truck.The 37's 302 was built for fuel mileage considerations with hi compression,mid range cam making high cylinder pressure at low speeds,lots of spark advance,lean low speed carb mixture and a heated intake.As I told Larry ,this is dicey business running the engine this way so keep an ear open for detonation.

PUSHRODS

Posted Sun October 12 2008 05:05 PM 11-1/8 is the longer rods used with Chevy style lifters? I got mine from Melling,the oil pump people.Tubular steel,stronger than stock for about 35 bucks. That being said,Smith makes an outstanding product from what I hear and will build any push rod you want. Here's a Ebay seller with the shorter tubular pushrods,maybe he has longer ones.

Posted Sun October 12 2008 07:46 PM It was 4 years ago and all I remember the box said Melling made in USA.I was using the typical Chevy lifters. Update....Try Rock Auto online,they have the 11.4 inch overall length Chevy pushrod,Sealed Power #RP3020,$2.58 each. I have bought from Rock Auto,super fast service.

SPEEDOMETER

Posted Fri March 24 2006 07:52 AM The speedo in my 37 Chevy PU partially dumped in it's trousers,the speedo needle worked fine,but the odometer got jammed inbetween numbers.I pulled it out,pretty easy job on a 37,disassembled the whole gizmo on the kitchen table.I then got an emergency electricial service call,when I came back,the shit had hit the fan.Seems our barn cat,who is generally outside wacking rodents,and who never jumps on tables when inside,jumped on the kitchen table and pushed all the little tiny pieces on the floor.Fuckin Cat Me and Joy managed to pick up all the odometer pieces,the dials and gears.After a few attempts I finally gor it reassembled properly and the sucker even works!!! Well, it works using a drill motor in reverse,with a wooden stick match chucked in the drill as a drive to test it. Now,lets see,American speedos indicate 60 mph at 1000 rpm cable speed,the drill data plate says 1100 rpm,so using a little high school algerbra to convert the formula,crap,I forgot how to do it,screw it,close enough

STARTER

Posted Mon December 08 2008 07:16 AM I sorta checked out the possibility awhile back.But the high compression 302 in the 37 Chevy I had turned over nicely with the same starter that was taken from a junker 56 Chevy car 12 years ago.Anyways,probably have to have a custom nosepiece built.Chevy small block V-8 have two flywheels ring gear tooth counts,153 and 168 depending on flywheel diameter.The starter location on the block is different on both,the starter drive is the same for both I believe unlike the 6's with a different starter drive for the two ring gears patterns.

Posted Tue October 19 2010 06:51 AM Yes,the starter came out of a rusted 56 Chevy car that was sinking into the earth.That was about 1996,I just bolted the starter to the engine in the 37 and that was that The problem sounds like a loose wire connection somewhere between the starter pushbutton and the solenoid or the solenod itself is bad.Or something else..................

STEERING BOX

Posted Thu August 21 2008 01:18 PM I put a 41-46 type box in my 37 several years ago.I cut the shaft and welded on a stub of the 37 shaft so I could use my existing steering wheel.A pick truck box has a shorter shaft that big trucks so keep that in mind when buying one unless you want to shorten the shaft. The difference in steering is quite noticable,much less friction.

SUSPENSION

Posted Wed September 30 2009 11:16 AM Rob,about time you started on that piece of shit .Sounds like it might be similar to the 37 Deerslayer,farmer hot rod.I'll tell ya what's in that that truck for a reference being they are somwhat the same.The 37 frame isn't boxed,but I added two additional crossmembers for stiffness.Old vehicles have stiff springs and flexy frames,better handling ones have stiff frames and springs that actually flex.You can box the frame on a truck ,but usually it's done on thinner car frames.Boxing is a good idea but very time consuming.Just make sure the frame is set up straight and level before welding.And read stuff on proper frame welding or you might create stress cracks.The 37 rear axle is a 57 Chevy car(they used this rear pumpkin behind 348-409 cars) with dearched Eaton springs and lowering blocks.The front suspension is a Durant monoleaf with two single leaves added and sway bar.Disc brakes on the front.Keep in mind the wheel bolt pattern differs,so pick something that matches front and rear or whatever before ordering wheels.A lot of guys use various 10 and 12 bolt GM rear from Novas and Camaros.Ford 9 inch is fine,not inexpensive if custom made to width.Most rear axles you'll find will need a complete rebuild for reliability,that makes a custom one sorta less expensive I suppose.Ken's truck rear suggestion is OK also if it ain't too wide. If you're engine doesn't have a full race 12 port set up you won't have issues with most typical trannys and rears from my experience.Me,You,Andy,Ken and others abused the 37 with the car rear and Saginaw 4 speed.Maybe the 37 has 220 hp,so go from there. For springs you should look at what Posie's offers.They have rear multileaf springs,I don't know about the front so check their site and give em a call. You're build will depend on how much chopping you want to do.If you want to keep the stock spring hangers and such,you're somewhat limited. And remember,if you're not gonna cruise long distances in the truck some stuff may not needed made to bullet proof specs.

Posted Wed October 27 2010 06:20 AM Jack,I put monoleaf springs in the front of the 37 Chevy that Larry owns now.They have been in there since 1997.I had to add two long leaves because I though it was too soft.The springs have poly front shackle bushings.A few guys here have driven the truck,I believe the ride is firm but less harsh than the stock spring pack.I think half the harsh ride is the metal bushings.

Posted Sat November 27 2010 06:48 AM I have heard a few stories of broken monoleafs.I put those in around 1997.They came directly from original manufacturer Durant.I talked to him personally and had the spring eyes rolled the other way from the production springs.

Posted Mon November 29 2010 08:59 PM Larry,Patrick Dykes had monoleafs listed in his catalog for a 37 1/2 ton.So I called him and he said Durant promised the spings but never delivered.Patrick gave me Durants business phone number to see if I could get a set.Durant was ok on the phone,sent me springs,I sent him money.The springs had reversed eyes that hit the frame at full suspension travel.I called again,sent back the springs and got a set with normal "uprolled" spring eyes.I think he paid the shipping .These cleared the frame but felt they were too soft for a truck so two long leaves from the original 37 springs were added.I don't know if Durant ever did make more than just a handful of springs to fit the 37 and whatever other years are the same spring. I do believe the early 30's Chevy car with a beam axle uses the same spring.

TIMING

Posted Sat July 05 2008 06:13 AM Ken,the total advance is figured on the engine making more power as it's advanced until the detonation threshold is reached.My 302 likes about 34 degrees total,with 12 of that being static timing set at idle.This is with 9.25 compression on a large chamber 302 head,93 octance pump fuel..Your engine's smaller 270 combustion chamber may need less advance because the mixuture may burn faster.My engine wants a little more timing,but it's at the limit of detonation at 34 degrees total. Although the vacuum adavnce doesn't apply at full throttle you may want to limit it's travel a little when increasing mechanical advance. Two types of detonation,the pinging heard when pulling a grade at part throttle isn't harmful to the engine so long as it not constant.Then there's the detonation at full throttle that you may not hear above the roar of the engine and exhaust.This style detonation can break pistons and destroy crank bearings if it continues long enough.Sometimes full throttle detonation can be felt as vibration that wasn't there before the timing was advanced more. If you're engine lacks a degreed damper pulley or flywheel,you may want to use a set back type timing light to see what goes on.I believe the stock mark on the flywheels is 5 degrees BTDC. But always tune the engine for what it likes,if the timing is more advanced or retarded than is should be,and the crankshaft doesn't fly onto the road,go with it.

TRANNY

Posted Sat July 19 2008 07:59 AM Arlyn,my light 37 with the 302 runs 2000 rpm at 70 mph in OD,PA type hills at highway speed are no problem.However running at lower speeds ,lets say 50 mph,the low rpm in OD sends a resounce through the truck.Most likely the way mine is tuned and the exhaust system. Carburated engines rely on manifold vacuum at part throttle to keep the fuel mixture vaporized properly for best economy.If you run too low an rpm,the throttle will be open more than necessary,the vacuum will be low,possibly even opening the hi speed enrichening circuit. It's nice if the vacuum goes no lower than about 10 inches at cruising speeds on the level and very slight hills. Modern fuel injected engines don't rely on manifold vacuum for vaporization,the low vacuum actually reduces pumping loses in the engine.

Posted Thu August 28 2008 03:08 PM Rob,when you drove my 37 it had a car Saginaw 4 speed,2.85 first gear with 3.36 rear axle.I like the lower numercialy gears to give more road speed through the tranny gears.My Saginaw had OD,I don't think you used it.Anyway,it can be buzzed along at 2800 rpm for hours on end if necessary.Saginaws,if you find a decent one,are rugged enough for an old truck that spins the rear tire(s) easily.I've redone many Saginaws,pretty easy to work on. My 37 has a Camaro T-5 in it now,2.95 first gear.The Camaro version has much closer gear ratios than the useless,at least with a torqey engine,S10 T-5's.T-5's are a bit marginal when getting near 300 lbs of torque.I upraded the tranny so it could handle the torque and swapped out 5th gear OD for another set that seemed more inline with the 302's cruise RPM.I got the T-5 for 50 bucks,then bought an S10 tranny for the more foward location of the shifter,rebuild kit,some gears,and 400 bucks later,a decent tranny. or you can buy a brand new 5 speed Tremac rated at 500 lbs of torque to bolt up to GM bellhousing for about 1800 bucks,ouch.

VIBRATION DAMPER

Posted Fri November 04 2005 06:38 AM When the vibration damper on my 302 failed,I contacted Dale Manufacturing in Salem Oregon about rebuilding the damper.Dale is the sole employee and owner,on the phone ,he was very informative.He said he had shop notes on the durometer reading of the original rubber GMC used,my damper would be better than new,the same durometer rubber and with a lifetime guarantee. I mailed it to him from NY on October 26 and recieved it back,good as new on November 3 rd.Great service,and a great price,102 bucks total with return shipping.

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Issued Monday February 16, 2009

Updated Monday September 12, 2016

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